How is fragile x syndrome caused

It is the most common inherited cause of intellectual disability. Fragile X syndrome is also linked to features of autism spectrum disorder. Fragile X syndrome affects around 1 in 3, boys and between 1 in 4, — 6, girls.

Fragile X syndrome causes a wide range of physical, developmental, behavioural and emotional difficulties although the level of severity between people with the condition varies enormously. Fragile X syndrome can cause a range of physical, developmental, behavioural and emotional difficulties in people. Although there is no typical presentation, some boys with Fragile X syndrome have a long narrow face, prominent forehead and large testicles.

The most significant effects of Fragile X syndrome are:. The level of severity of these effects varies considerably and not every person with Fragile X syndrome will have every one of these characteristics. This gene produces a protein that helps the brain to function normally.

If this gene is changed or altered in any way, it cannot produce its normal protein, which can result in Fragile X syndrome. Fragile X syndrome is inherited in a way that is known as 'X-linked', as the changed gene is on the X chromosome. This means that men with Fragile X syndrome are often more severely affected than women.

This is because men only have one X chromosome, whereas women have two X chromosomes, only one of which is changed. Although Fragile X syndrome is not that common, affecting around 1 in 3, boys and between 1 in 4, — 6, girls, the number of men and women who are carriers of the Fragile X gene is significantly higher. It is estimated that 1 in women and 1 in men are carriers of the gene.

These people are known as 'Fragile X pre-mutation carriers'. Pre-mutation carriers may not have any symptoms of Fragile X syndrome but they are at risk of passing on the changed FMR1 gene and having a child or grandchild with Fragile X syndrome. People who are Fragile X pre-mutation carriers may also be at risk of developing health problems later in life. Around 20 per cent of female Fragile X pre-mutation carriers experience reduced fertility or early menopause.

These conditions are called Fragile X-associated Disorders. Fragile X syndrome and Fragile X-associated disorders can only be diagnosed by DNA testing — usually by a blood test but sometimes via cheek swab or mouthwash. If possible, testing should be done at a recognised genetics service. If there is a diagnosis of Fragile X syndrome, it is important that immediate and extended family members are also tested to identify others who may have the changed FMR1 gene.

Contact the Fragile X Program Fax Request an Appointment Request a Second Opinion. Fragile X Syndrome. What is fragile X syndrome? These can include: intellectual disability hyperactivity or attention deficit disorder ADD anxiety autism spectrum disorder seizures hypotonia Some children with fragile X may also have mildly characteristic features such as prominent ears.

What are the symptoms of fragile X syndrome? What are the causes of fragile X syndrome? Are there any medical concerns with fragile X? FXS can cause learning disabilities, developmental delays, and social or behavioral problems.

Disabilities vary in severity. Boys with FXS usually have some level of intellectual disability. Girls may have some intellectual disability or learning disability, or both, but many with fragile X syndrome will have normal intelligence. They might only be diagnosed with FXS if another family member is also diagnosed. People with FXS may show a combination of the following symptoms as children and throughout life:. The X chromosome is one of two types of sex chromosomes.

The other is the Y chromosome. Women have two X chromosomes while men have one X chromosome and one Y chromosome. The defect, or mutation, on the FMR1 gene prevents the gene from properly making a protein called the fragile X mental retardation 1 protein. This protein plays a role in the functioning of the nervous system. The exact function of the protein is not fully understood.

A lack or shortage of this protein causes the symptoms characteristic of FXS. Being a fragile X permutation carrier can increase your risk for various medical conditions. Let your doctor know if you think you may be a carrier or if you have a child with FXS.

That will help your doctor manage your care. Women who are carriers are at an increased risk for premature menopause, or menopause that starts before the age of FXTAS causes a tremor that gets increasingly worse. It also can lead to difficulty with balance and walking. Male carriers may also be at an increased risk for dementia. Children who show signs of developmental delays or other outward symptoms of FXS, such as a large head circumference or subtle differences in facial features at a young age, may be tested for FXS.

The average age of diagnosis in boys is 35 to 37 months. In girls, the average age of diagnosis is Depending on the results, your doctor may choose to do additional testing to determine the severity of the condition.